Titanium oxide having a monoclinic β-type structure represented by TiO2(B) has recently attracted attention as an active material for a non-aqueous electrolyte battery (see JP-A 2008-34368 (KOKAI), JP-A 2008-117625 (KOKAI) and WO 2009/028553 A1). Spinel type lithium titanate (Li4Ti5O12), which is currently in practical use, is limited to 3 in the number of lithium ions which can be inserted and desorbed per unit chemical formula. For this reason, the number of lithium ions which can be inserted and desorbed per titanium ion is ⅗ (0.6) which is a theoretical maximum. In the case of TiO2(B), on the other hand, the number of lithium ions which can be inserted and desorbed per titanium ion is 1.0 at maximum. Therefore, TiO2(B) has a theoretical capacity as high as about 335 mAh/g.
However, the practical electrode capacity of TiO2(B) is about 170 to 200 mAh/g, which is significantly lower than the theoretical capacity as disclosed in JP-A 2008-34368 (KOKAI) and JP-A 2008-117625 (KOKAI). It is thought that this is because, though there are many sites which can serve as Li hosts in a crystal structure of TiO2(B), effective mobile Li ions are reduced because the diffusibility of Li ions in a solid is low.